San Ramon, CA – March 12, 2010
ENGEO has won a California Geotechnical Engineering Association (CalGeo) 2009 Outstanding Project Award for its Trestle Glen project in Colma (San Mateo County), California. Trestle Glen is a mixed-use, mixed-income, transit-oriented urban reuse development on 1.7 acres that now offers 119 units of affordable housing along with commercial and light industrial options adjacent to the Colma Bay Area Rapid Transit (BART) Station. The project was a public-private partnership between BRIDGE Housing (a non-profit developer) and the County of San Mateo. The ground improvement system that ENGEO employed was used for the first time in Northern California to mitigate liquefaction potential. ENGEO combined recent advances in liquefaction evaluation with pre- and post-ground improvement testing to verify that the project design criteria were met. ENGEO also worked closely with the other members of the project design team, including the owner, the general contractor, and the ground improvement contractor to collect the geotechnical data for analysis in a time-efficient manner and to successfully complete the project.
ENGEO’s geotechnical exploration found that relatively shallow groundwater and potentially liquefiable deposits underlie the site. ENGEO’s innovative approach to mitigate the site included installing Rammed Aggregate Piers (RAPs) to improve the foundation support and to mitigate potential liquefaction where deep deposits of loose/soft soils extended below the proposed structure. Further, ENGEO implemented a pre- and post-ground improvement Cone Penetration Test (CPT) program to evaluate the post-ground improvement liquefaction and seismic settlement potential. The results of ENGEO’s data analysis showed that RAP installation improved the site by effectively mitigating liquefaction potential and by significantly reducing associated settlements.